Hyperhidrosis is the medical term for excessive sweating. People with hyperhidrosis may sweat even when they are cool or when they are at rest. For many people with this condition, excessive sweating occurs unpredictably, even without the normal triggers of temperature, exercise or in response to situations that make them uncomfortable. In most cases, there is no cause to be found, although it can run in families. Most people consider that it is caused by overactive sweat glands. No matter the cause, uncontrolled sweating can take an emotional and physical toll for those who experience it.